This invention relates to filter assemblies for use in supplying extremely clean air to rooms and work stations where operations are being conducted on materials or in connection with processes for which the introduction of any extraneous particles or impurities must be carefully avoided.
Such clean air installations sometimes involve the provision of a clean air supply for an entire clean air room. In other cases, it may be necessary only to provide a clean air supply at a particular bench or work station, within a room for which a normal air supply is otherwise used.
Some prior clean air work stations and a room air cleaner are shown, for example, in U.S. Pat. Nos. 3,494,112; 3,703,801; and 3,802,168; assigned to the same assignee as the present invention. Other clean room arrangements and filter assemblies are shown in U.S. Pat. Nos. 3,158,457; 3,418,915; and 4,178,159. Details of other prior work station arrangements and of filter elements and assemblies are also shown in U.S. Pat. Nos. 3,318,076; 3,470,679; 3,616,624; and 3,729,905.
Prior filter units for such installations have involved various problems, such as the blocking of some of the possible filter area by the necessity of providing clamping mechanisms to hold such filters removably in place, and by problems of securing a perfect gasket or other seal all around a filter unit to avoid the bypassing of undesired particles around the filter from a structurally separate pressurized plenum chamber with which such prior filters have been removably connected. Prior filter units in which the filter material is clamped mechanically inside a thick frame of wood or other flammable material may also present unacceptable fire hazards in connection with installations.
Thus, applicants have perceived a need for an improved filter assembly as described and claimed in this application.